Conventionally, an engine and a transmission are integrally provided in a saddle type vehicle, such as a motorcycle, and the vehicle is configured to utilize engine oil for lubricating a speed change gear train. For example, an engine for a motorcycle described in Patent Document 1 includes an oil pump mechanically driven by a crankshaft. The oil discharged from this oil pump passes through an oil filter and an oil cooler, and thereafter, is fed to a main passage within a crankcase. Then, while being fed from the main passage to a valve operating system, a piston, a crank journal, and the like of the engine, the oil is also supplied to a transmission through a transmission side oil passage.